EDINBURGH, Scotland, March 11 (UPI) -- The 1988 Lockerbie jetliner bombing was payback for the U.S. Navy's downing of an Iranian airliner six months earlier, an ex-Iranian intelligence officer says.

Abolghassem Mesbahi says Iranian Supreme Leader Ayatollah Khomeini ordered the attack on Pan Am Flight 103 over Lockerbie, Scotland, in which 290 people died, to avenge the accidental shooting down of Iran Air Flight 655 over the Persian Gulf by the USS Vincennes and left 270 people dead, the Daily Telegraph reported Monday.

The London newspaper said previously unreleased evidence that was to have been used in an appeal hearing for Abdelbaset al-Megrahi, the former Libyan intelligence officer convicted of the bombing, supports Mesbahi's contention. The Lockerbie bombing was carried out by the Popular Front for the Liberation of Palestine -- General Command, the newspaper said the evidence suggests.

The Telegraph said documents obtained by the Arab television network al-Jazeera for a documentary called "Lockerbie: What Really Happened?" names key individuals allegedly involved in the attack.

The Telegraph said the new evidence puts the conviction of al-Megrahi in question and supports allegations the truth about Lockerbie was covered up by Britain and the United States to avoid angering Syria, a key player in the Middle East

Al-Megrahi, the only man convicted in the Lockerbie attack, dropped his appeal after being released from prison in 2009 because he was suffering from cancer, though he maintained his innocence until his death in 2012.

Al-Megrahi's conviction was based on the prosecution's theory that Libyan leader Moammar Gadhafi had personally ordered the Lockerbie attack in retaliation for the U.S. bombing of Tripoli and Benghazi in 1986, in which Gadhafi's daughter was killed.

"Iran decided to retaliate as soon as possible," Mesbahi, who had reported directly to Iranian President Akbar Hashemi Rafsanjani and now lives under a witness protection program in Germany, told al-Jazeera. "The decision was made by the whole system in Iran and confirmed by Ayatollah Khomeini.

"The target of the Iranian decision-makers was to copy exactly what happened to the Iranian Airbus. Everything exactly the same, minimum 290 people dead."

The newspaper reported the U.S. State Department said it wanted all those responsible for the Lockerbie attack brought to justice, while Britain's Foreign Office said the case remains open because investigators believe al-Megrahi didn't act alone.

The Iranian government had no comment on the documentary's findings, but has previously denied any involvement in the bombing of Pan Am Flight 103.